OSLO (Reuters) – Finland’s nuclear regulator has identified a safety issue at Olkiluoto 3, a 1.6-gigawatt reactor built by France’s Orano, and the problem needs to be fixed before the unit can receive a permit to operate, the regulator told Reuters.

The reactor is due to start producing electricity in January next year after a decade-long delay.

Part of the pressuriser, a primary circuit component of the reactor, is vibrating at levels that exceed safety limits, said Pekka Valikangas, the regulator’s section head for nuclear reactor regulation.

“The test results show that these vibrations are not approved,” he said in an interview.

“This must be taken care of before the ministry decides on the permit,” Valikangas said, adding that the regulator would offer two options for a solution. The reactor’s owner, Finnish consortium TVO, and supplier Orano, previously known as Areva, would need to choose from those options.

Finland needs the reactor as it imports more than 25 percent of its electricity from neighbouring Sweden and Russia, while its energy needs are growing.